1. Field of the Invention
The present invention relates to a structure of a cross roller bearing which consists of an outer race, an inner race and a large number of rollers trapped between raceway grooves of the outer and inner races.
2. Description of the Prior Art
Conventional cross roller bearings, as shown in FIG. 8, include an inner race 1 having a V-shaped groove 2 formed by inclined raceway surfaces 5; an outer race 4 consisting of two divided races 4a, 4b each of which has an inclined raceway surface 5 to form an inverted V-shaped groove 20; a raceway 13 formed by the V-shaped groove 2 of the inner race 1 and the inverted V-shaped groove 20 of the outer race 4; and rollers 6 as rolling elements guided by retainers 10. In the cross roller bearing, the rollers 6 in the raceway 13 are arranged in such a way that the adjacent rollers cross each other. The cross roller bearing withstands radial loads and two-way axial loads. The rollers 6 are assembled into the raceway 13 between the inner race 1 and the outer race 4 by forming a bolt insertion hole 17 through the divided races 4a, 4b of the outer race 4, placing the rollers 6 between the inner race 1 and one of the divided races 4a, mounting the other divided race 4b in place, and fastening the divided races 4a and 4b with bolts 18 and nuts 19.
Examples of such cross roller bearings include one disclosed in the Japanese Utility Model Laid-Open No. 95228/1985.
Other known examples of the cross roller bearings use embedded bolts and rivets, in place of bolts and nuts, to assemble the divided outer races.
Such cross roller bearings, however, have the following drawbacks. When the cross roller bearing is assembled by dividing the outer race 4 into a pair of races 4a, 4b, placing the rollers 6 between the inner race 1 and one divided race 4a, mounting the other divided race 4b, and fastening the divided races 4a and 4b together, fixing tools such as bolts, nuts and rivets to hold the divided races 4a, 4b immovable are required. It is also necessary to form insertion holes in the outer race 4 through which to insert the fixing tools such as bolts and nuts. This in turn increases the manufacturing cost and the number of parts. It should also be noted that portions where the insertion holes for the fixing tools are formed constitute a wasted space not functioning as a bearing.
In the cross roller bearing whose outer or inner race is divided in two, if the fixing tools for fastening the divided races can .be eliminated, there is no need to form the insertion holes for the fixing tools in the divided races. This increases the strength of the divided races and, because additional space is not needed for the insertion holes in the divided races, the size of the divided races can be reduced to that extent, permitting effective use of the space. In other words, to the extent that the insertion holes for the fixing tools are not required, the outer diameter of the outer race can be made smaller when the outer race consists of the divided races. If the outer diameter of the outer race remains the same, it is possible to increase the pitch circle of the rollers as well as the number of rollers. It is also possible to maintain a good balance in strength between the outer and inner races.